Growth and physical properties of metallic In₂O₃ single crystals

Single crystals of metallic indium oxide were grown for the first time by molten salt electrolysis and their electrical and magnetic properties were investigated. The crystals are the cubic form of indium oxide with a C-type rare earth oxide structure as inferred by X-ray powder diffraction. The crystals are highly reflective and have colors ranging from dark green to green-yellow depending on the crucible used for preparation and on the location of the crystals at the cathode surface. The resistivity as a function of temperature, on all the crystals, showed metallic behavior up to about 100 K and almost temperature-independent behavior down to ∼2 K. The room temperature resistivity of the dark green sample is in the range of 10^-4 Ω-cm. Qualitative Seebeck measurements indicate that electrons are the primary charge carriers. The temperature variation of the magnetic susceptibility is Pauli paramagnetic, consistent with the observed metallic property. The crystals were found to be stable up to ∼1200 K upon exposure to oxidizing atmospheres. The measured physical properties are supportive of the presence of a small concentration of charge carriers with high mobilities.